Field of the Invention
The present invention relates to a control device switching system for switching a control device that performs communication between a plurality of control devices that are incorporated in a vehicle and connected to each other via a common communication line.
Description of the Background Art
A plurality of control devices called ECUs (Electronic Control Units) are incorporated in a vehicle. Those control devices perform transmission and reception of information via a common communication line to achieve the operations of the vehicle in cooperation with one another. These control devices are supplied with electric power from a battery, an alternator/motor, and the like that are incorporated in the vehicle. However, as the number of the control devices incorporated in a vehicle increases in recent years, the amount of electric power consumed by the control devices tends to increase accordingly. When the amount of power consumption increases, the amount of power to be generated by the alternator and the like also increases, leading to poorer fuel economy of the vehicle. For this reason, lower power consumption is demanded for vehicles, and the control devices are also needed to accommodate the needs for lower power consumption.
Conventionally, various techniques have been employed for the control devices to accommodate the needs for lower power consumption. Primary examples of the techniques include cutting off the power supply to the control devices that do not need to start up, and putting the control devices into a sleep state. However, in a network provided with an abnormality sensing device, a control device that does not perform data reception for a predetermined duration may be regarded as having a trouble, and an abnormality process may be started therefor.
In order to resolve such a problem, Patent Document 1 provides a transmission-reception control device having the function to stop the transmission and reception function of another control device among a plurality of control devices connected to a network by cutting off the power of the other control device or putting it into a sleep state. The transmission-reception control device executes, as a substitute, the data transmission that should be performed by the target control device whose transmission and reception are stopped. Thereby, the power consumption of a vehicle is reduced without causing the abnormality sensing device for sensing data abnormality in the network to detect abnormality.    [Patent Document 1] JP-A-2013-6454
In Patent Document 1, the transmission-reception control device stops the transmission and reception of the target control device and thereafter takes over the data transmission that should be performed by the target control device, as described above. However, when the transmission-reception control device is out of order or is under a high processing load, or when it is executing other important processes, an event occurs that the transmission-reception control device cannot substitute data transmission. This event is detected as a network failure by the abnormality sensing device. Moreover, if the transmission-reception control device is forced to take over the data transmission to be originally performed by the target control device while the transmission-reception control device is under a high processing load or performing an important process, the transmission-reception control device loses its real-timeness, resulting in a failure in the behaviors of the vehicle.